Test wells drilled

Jan. 21, 2007

By Russell Stigall

Frontiersman

MAT-SU - A major unknown in the viability of the Point MacKenzie prison site is whether the water from its wells will spring forth eternal - or at least for the expected 50-year lifespan of the 2,251-bed facility.

During the site-selection process, hydrogeology firm Shannon & Wilson reviewed Department of Natural Resources well logs for the Point Mac site, said Bill Burgess, senior associate, geotechnical leader for Shannon & Wilson.

&#8220We wanted to assess what was the likelihood that we could produce the amount of water we needed,” Burgess said.

The records showed that several test wells were drilled in the 1980s and 1990s. These 5- and 6-inch-diameter wells were sunk to depths of between 135 and 400 feet. The test wells pumped as high as 200 gallons per minute, but they had 100 percent draw-down in only a couple of hours, Burgess said.

&#8220Pumping a well fast is a good idea if you are trying to clear the well of debris, but it doesn't get you all of the information you need from an engineering point of view,” Burgess said. &#8220We're looking for a sustainable rate of flow,” he said.

Even poor water quality or supply won't derail the project at this stage of the game.

&#8220At this point, it is probably a matter of engineering around it,” Burgess said.

Burgess described, as an example of engineering, a farmer living near the site. The farmer sunk a series of small wells in a circle and pumped the sand out from around each well. This left a large collection cauldron underground, which the farmer tapped by way of a main well in the center.

The project's design/build contractor will face difficulty nonetheless.

Burgess said he had experience with wells running dry near the selected prison site. In years with low snowpack, wells tapped into a shallow aquifer went dry around Millers Reach.

This can be avoided by drilling a deeper well, if the necessary quality and quantity of water is there, Burgess said.

The engineering and surveying firm Tryck Nyman Hayes, Inc. is in charge of the test well project.

The prison will require a huge water storage capacity due to fire and emergency requirements, said Norm Goocher, manager with Tryck Nyman Hayes. Regardless of the rate of water flow from the wells, Goocher said, the 160-acre site will need to house a well field.

Goocher said he feels confident the necessary water supply will be at the Point Mac sit, but that he could be surprised.

&#8220It is up to geology - and luck and depth,” Goocher said.

The engineering and surveying firm expects to get results back by the end of January, Goocher said. Although work is weather dependent, he said, and if it gets too cold, crews can't drill.

Tryck Nyman Hayes contracted geotechnical and environmental consultants Shannon and Wilson Inc. for the test's hydrogeology assessment. The firm will study: the distribution and movement of the site's groundwater; the amount of solids coming up in the water, called turbidity; and the water's hardness - the amount of material in the water that remains in solution until a change in pressure and temperature deposits the solute onto pipes and plumbing.

Burgess said his firm will characterize the general conditions as accurately as they can so the design-build contractor can work with a reasonable risk.

&#8220They have to put brackets around it, or else they have huge contingency costs,” Burgess said.

Between Palmer South, Sutton and Point Mac - three of the four final proposed prison sites - Point Mac has the highest risk with regard to water supply. Palmer has city-supplied water, and Sutton has high-yield pre-existing wells.

Anchorage gets most of its water supply from a deep aquifer at artesian pressures. Currently, no wells go deep enough at Point Mac to know if Anchorage artesian pressure extends to that area. Artesian pressures go at least out to midchannel of the Knik Arm, Burgess said.

The prison's water supply will need to go through treatment, Burgess said, at least filtration. Public water supplies must be treated.

The test well drilled this weekend at Point Mac is a pilot well, not a production well, Burgess said.

Contact Russell Stigall at

352-2267 or russell.stigall@ frontiersman.com